# Refraction and its connection quantum gravity

1. Jul 22, 2013

### fet2105

For a while I have wondered if the refraction of light had any connection to gravity on small scales (dare I say . . . quantum gravity?!?). I found this paper in the Cornell University Library. Below is the link and a copy of the opening synopsis that anyone can see without downloading it. . . . Is the "effective refractive index" a mere coincidence of their words with my thoughts? Any thoughts anybody?

"Effective refractive index tensor for weak field gravity

Petarpa Boonserm, Celine Cattoen, Tristan Faber, Matt Visser, Silke Weinfurtner (Victoria University, New Zealand)
(Submitted on 8 Nov 2004 (v1), last revised 18 Mar 2005 (this version, v2))
Gravitational lensing in a weak but otherwise arbitrary gravitational field can be described in terms of a 3 x 3 tensor, the "effective refractive index". If the sources generating the gravitational field all have small internal fluxes, stresses, and pressures, then this tensor is automatically isotropic and the "effective refractive index" is simply a scalar that can be determined in terms of a classic result involving the Newtonian gravitational potential. In contrast if anisotropic stresses are ever important then the gravitational field acts similarly to an anisotropic crystal. We derive simple formulae for the refractive index tensor, and indicate some situations in which this will be important."

quote taken from:http://arxiv.org/abs/gr-qc/0411034

2. Jul 22, 2013

### DrChinese

The short answer is no.

The usual refraction of light is not a function of gravitational forces. This is instead a electromagnetic field effect which is a function of the material the light is passing through (and the effective speed of light in that material).

There are gravitational effects that can do much the same thing, but these are seen only in the large scale (as per the article you reference). This is because gravity can slow light, but is relatively weak - and therefore requires the presence of a lot of mass to exert much effect.